The present invention relates generally to lures for attracting and controlling Diabrotica species. In particular, the invention relates to lures comprising one or more compounds found in the volatile fraction of Cucurbita blossoms, or analogs thereof, alone or in combination with other lures, insecticides, and/or compulsive feeding stimulants.
The chrysomelid genera Diabrotica and Acalymma contain numerous pest species, including the western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte; the southern corn rootworm (SCR) or, the spotted cucumber beetle, D. undecimpunctata howardi [D. duodecimpunctate Fab.]; the northern corn rootworm (NCR), D. barberi Smith and Lawerence; and the striped cucumber beetle (SCB), Acalymma vittatum (Fabr.).
The western, norther, and southern corn rootworms are the most expensive insect pests of North America and annually cost U.S. farmers approximately one billion dollars in costs associated with lost crop yield and with preventative treatments with soil insecticides. The era of relatively inexpensive crop protection against these pests has ended because of generalized rootworm resistance to organochlorine insecticides and the withdrawal by the U.S. EPA of registrations for these insecticides due to widespread environmental contamination. The newer organophosphorous and carbamate insecticides are more expensive and subject to accelerated microbial degradation in soils and a rapid loss of activity. Furthermore, due to the persistence of many of these soil insecticides, groundwater and surface run-off pollution is of much concern to state and federal agencies. Because of the uncertain performance and safety of the major products currently used for larval rootworm control, such as carbofuran (Furadan(trademark)), isofenphos (Amaze(trademark)), phorate (Thimet(trademark)), terbufos (Counter(trademark)), a technological void exists for controlling these pests. Even standard cultural methods of pest management such as crop rotations of corn-soybean-corn and corn are endangered as evidence exists that the northern corn rootworm can undergo an extended diapause for two seasons. Hence, the benefits of yearly crop rotation are threatened.
Present soil insecticide technology for corn rootworm control is rapidly becoming unworkable. The use of volatile attractants, singularly and in combinations with other control methods, can become the basis for a new integrated pest management IPM) technology for rootworm control that is economically favorable for the farmer and certainly much less environmentally objectionable. In this regard, Diabrotica and Acalymma are known to show a close association with host plants of the family Cucurbitaceae, particularly with the genus Cucurbita. Adult beetles are most commonly found in the blossoms of Cucurbita species where they feed on pollen (in staminate flowers) and on nectar. In most instances, adult beetles showed a preference for the blossoms of C. maxima Duchesne cultivars over those of C. pepo L. and C. moschata Poir.
The blossom characteristics, i.e., color, size, shape, and/or fragrance, responsible for this preference are not fully understood, although Diabrotica attraction to certain compounds, termed semiochemicals, has been reported. By way of background, semiochemicals are plant-produced compounds which act by diffusion through air to produce behaviorial responses in associated insect species. Kairomones are those semiochemicals which act to benefit the receiving species; allomones are those which benefit the sending species; and synomones, e.g., floral volatiles involved in pollination, benefit both the emitting plant, through pollination, and the perceiving insect by rewards of nectar and pollen or through more intangible ecological rewards of aggregation or lek formations which lead to mating.
One of the earlier reports relating to Diabrotica attraction to compounds appeared in Morgan, et al., J. Econ. Entomol., 21:913 (1928). This collection of preliminary results on the chemotropic response of certain insects included the observation that the spotted cucumber beetle, D. undecimpunctata howardi (as D. duodecimpuntata Fab.), was attracted to cinnamaldehyde and cinnamyl alcohol. These results were obtained using white granite-ware pans of about 2-quart capacity set in rows on stakes 2 feet high, and filled with 1 quart of water to which was added 1 cc. of the chemical to be tested. The areas in which experiments were conducted included a field white with the blossoms of the field daisy (Erigeron annuus) oatfields, margins of woods, hedge rose, a cane brake, a slaughter-house lot; and a livery-stable yard. There is no indication in the reference as to the degree to which, or the conditions under which, cinnamic aldehyde and cinnamic alcohol acted as attractants. Shapp, et al., J. Econ. Entomol., 22:98 (1929) disclosed a preliminary report indicating that the spotted cucumber beetle was attracted by oil of thyme (white) and benzyl alcohol. However, in tests by Lampman, et al, J. Chem. Ecol., 13:959 (1987) benzyl alcohol was shown to have negligible attractant value.
Ladd, et al., J. Econ. Entomol., 76:1049 (1983), studying a mixture of phenethyl proprionate, eugenol, geraniol, a food-type lure for Japanese beetles, reported that eugenol was attractive to adults of D. barberi Smith and Lawrence (NCR), but not attractive to D. virgifera virgifera LeConte (WCR). Ladd, T. L., J. Econ. Entomol., 77:339 (1984) tested nine compounds closely related to eugenol for attractancy to NCR including four groups: eugenol and its close relatives with isomeric or saturated hydrocarbon side chains; eugenol acetate and its isomer; anethole and its analogs with isomeric or saturated side chains; and a miscellaneous group consisting or methyleugenol and 2-allyl-6-methoxyphenol (orthoeugenol). The author reported two new attractants for NCR, isoeugenol and 2-methoxy-4-propylphenol and concluded that while neither the position of the double bond in the side chain nor the degree of saturation appeared critical in attracting NCR the presence of the methoxy and hydroxyl groups at their respective positions (adjacent), particularly the latter, seemed to be important. Yaro, et al., Environ. Entomol., 16:126 (1987) reported that eugenol and 2-methoxy-4-propyl phenol were highly attractive to D. cristata Harris ( a non-pest species) and D. barberi Smith and Lawrence, whereas isoeugenol acetate was not attractive. None of the compounds was highly attractive to D. virgifera vigifera LeConte. Ladd, et al., J. Econ. Entomol., 77:652 (1984) also conducted tests to study the influence of color and height of eugenol-baited sticky traps and reported that the traps were most effective when painted yellow and placed 0 to 0.25 m above ground.
Another recent report of investigations concerning a chemical basis for Diabrotica orientation to the blossoms or foilage of Cucurbita species was in Andersen, et al., J. Chem. Ecol., 12:687 (1986). The authors screened C. maxima xe2x80x9cBlue Hubbardxe2x80x9d blossom volatiles for electroantennogram (EAG) activity, a laboratory test for insect electrophysiological response to volatile compounds, and found two fractions had significant activity for the southern corn rootworm. The first peak consisted of indole and the second, smaller peak, was not characterized. Indole was then field tested for insect responsiveness and found to be a potent attractant of the western corn rootworm and of the striped cucumber beetle. However, the southern corn rootworm was not attracted at any dosage level despite the strong EAG response.
Anderson, et al., J. Chem. Ecol., 13:681 (1987) subsequently characterized the blossom constituents of attractive Cucurbita floral volatiles from a number of cultivars representing C. moschata, C. pepo, and C. maxima, and examined other factors, including nutritional and secondary chemical characteristics, that might influence beetle field distribution in blossoms. They found paradimethoxybenzene to be a major constituent of headspace samples from cultivated Cucurbita cultivars. The Diabrotica species showed a clear preference for certain cultivars. SCR preferred the blossoms of C. maxima cultivars, while WCR preferred the cultivars of C. maxima as well as a single cultivar of C. pepo. The authors suggested that NCR and SCR are similar in their most preferences, each strongly favoring C. maxima, whereas WCR appeared to find a broader range of cultivars acceptable. No firm conclusions were reached with respect to whether the gustatory cues, i.e., the levels of cucurbitacins, and olfactory cues, i.e., floral odors and level of release, acted individually or in concert, along with visual qualities to produce the patterns of preferences exhibited by the various species of Diabrotica.
Seasonal variations in responses to attractants have also been observed. As noted earlier, Andersen, et al., J. Chem. Ecol., 12:687 (1986) found that indole elicited a strong EAG response from SCR, but was wholly ineffective as an attractant in field tests. However, Lampman, et al., J. Chem. Ecol., 13:959 (1987) subsequently found that indole was in fact a moderately active attractant for SCR late in the season. In that study, the authors field tested various blossom volatiles and related compounds and found that southern, western, and northern corn rootworm adults exhibited not only a species specific response but also a seasonal pattern of response to sticky traps baited with various benzenoid compounds. SCR adults were attracted in early to mid-August to traps baited with veratrole (1,2-dimethoxybenzene), phenylacetaldehyde, and chavicol (4-hydroxy-1-allylbenzene). In late August and September, SCR trap catches dramatically increased for veratrole and phenylacetaldehyde, as well as for some compounds previously unattractive compounds, such as indole, several eugenol-related compounds, benzyl acteone, and phenethyl alcohol. WCR adults were significantly attracted to a different group of compounds, namely estragole, trans-anethole, and indole. Estragole (4-methoxy-1-allylbenze) was an effective WCR attractant from early August until the end of the trapping period in late September and early October. Indole and trans-anethole (4-methoxy-1-propenylbenzene) were less effective attractants than estragole and were most active at the begining and/or end of the corn sesason. The para-methoxy ring substituent and the position of the double bond in the propanoid side chain were noted to be critical for maximum WCR response; compounds differing in either aspect were less attractive. The phenyl propanoids, eugenol and isoeugenol, significantly attracted NCR adults. Ladd, T. L., J. Econ. Entomol., 77:339 (1984) previously found that NCR response is optimal for phenylpropanoids with a meta-methoxy and para-hydroxy substituent. Both Ladd, supra, and Lampman, et al., supra, noted a seasonal variability in response to eugenol and isoeugenol.
A comparison between the rootworm species indicated that the ecologically similar NCR and WCR adults are attracted to structurally related phenylpropanoids and both species respond to changes in the ring substituents of the major attractants. However, WCR and NCR adults are not attracted to the same phenylpropanoids, although SCR adults are occasionally attracted to indole (a WCR attractant) and to eugenol and isoeugenol (NCR attractants). The authors in Lampman, et al., supra, also noted (and subsequently reported in Metcalf, et al., J. Econ. Entomol., 80:870 (1987)) an increase in SCR trap catch for either eugenol or veratrole added to insecticide-impregnated cucurbitacin baits. Apparently, SCR adults cross-responded (especially late in the season) to some WCR and NCR attractants, although the main attractants for each species was highly specific.
The foregoing results suggested that Diabrotica are attracted to certain single component attractants; however, none of these attractants demonstrated the requisite degree of attraction required to effectively control and manage populations of Diabrotica. Thus, there exists a need in the art for an alternative safe and effective method for management of Diabrotica species which is effective in controlling the more visible stage of the insect pests, i.e., the adult, yet which is economical and which abolishes the need for the use of soil insecticides.
The present invention provides novel attractants for the control of Diabrotic species insects, novel mixtures of attractants and novel compositions including, in combination, Dibrotica species attractants, diabroticiticidal insecticides and compounds and compositions functional as compulsive stimulants of Diabroticite feeding behavior.
Novel attractants provided according to the invention include: xcex2-ionone; 4-methoxycinnamaldehyde; 4-methoxycinnamonitrile; 4-methoxy-1-vinyl-benzene; 4-methoxy-1-propyl-benzene; 4-methoxy phenyl ethyl ether; 4-methoxy phenyl acetonitrile; allyl benzene; cinnamonitrile; 2-methoxy cinnamaldehyde; cinnamyl acetate; cinnamic acid methyl ester; dihydrocinnamyl aldehyde; and phenyl propionitrile.
Also provided are the following novel attractants: 4-methylphenylethanol, 4-chlorophenylethanol, 4-fluorophenylethanol, phenylethanol, phenylpropanol, 4-methoxyphenylethanol, 3-methoxyphenlyethanol, 2-methoxyphenylethanol, 4-methoxyphenylpropanol, phenylethylamine, and phenylpropylamine.
These novel attractants are suitable for use individually or in combination with each other or known Diabrotica species attractants.
Novel mixtures of attractants according to the invention are seen to include a compound selected from the group consisting of dimethoxybenzene, trimethoxybenzene, and guaiacol admixed with one or more compounds selected from the group consisting of indole, phenylacetaldehyde, anethole, eugenol, cinnamaldehyde and cinnamonitrile. Presently preferred dimethoxybenzene compounds include orthodimethoxybenzene (xe2x80x9cveratrolexe2x80x9d) as well as the meta- and para-forms. Of the isomeric forms of trimethoxybenzene, the 1,2,4-trimethoxy form is preferred. Presently preferred attractant mixtures include the following: veratrole and indole (VI); veratrole and phenlyacetaldehyde (VP); veratrole, indole and phenylacetaldehyde (VIP); meta-dimethoxybenzene, indole and phenylacetaldehyde (mDMBIP); para-dimethoxybenzene, indole and phenylacetaldehyde (pDMBIP); veratrole, indole, phenylacetaldehyde, anethole and eugenol (VIPAE); trimethoxybenzene, indole, and cinnamaldehyde (TIC); trimethoxybenzene and indole (TI); trimethoxybenzene and cinnamaldehyde (TC); and quaiacol, indole and phenylacetaldehyde (GIP).
Alternately, constituted attractants for Diabrotica species according to the present invention are selected from the group consisting of the following mixtures: cinnamaldehyde indole (CI); xcex2-ionone and indole (BI); and xcex2-ionone and cinnamaldehyde (BC).
According to another aspect of the invention, compounds effective as attractants for southern corn rootworm include; meta-dimethoxybenzene, paradimethoxybenzene, indole, phenylacetaldehyde, trimethoxybenzene, 1,2,4-trimethoxy benzene, transcinnamaldehyde, allyl benzene, cinnamonitrile, 4-methoxy cinnamaldehyde, cinnamyl acetate, phenyl propionitrile, and phenyl ethanol. Particularly useful are unsubstituted phenylpropanoids having an unsaturated side chain, and having an aldehydic carbonyl group or a nitrile group at the free terminus of said side chain.
Compounds herein shown to be effective as attractants for western corn rootworm include: trimethoxybenzene, 1,2,4-trimethoxybenzene, indole, cinnamaldehyde, trans-cinnamaldehyde, xcex2-ionone, estragole, trans-anethole, 4-methoxy-1-vinyl benzene, 4-methoxy-1-propyl benzene, 4-methoxybenzyl methyl ether, 4-methoxyphenyl ethyl ether, 4-methoxyphenyl acetonitrile, 4-methoxycinnamonitrile, cinnamonitrile, 4-methoxy cinnamaldehyde, 2-methoxy cinnamaldehyde, cinnamyl acetate, and cinnamyl alcohol. Particularly useful are phenylpropanoids having a para-methoxy group, having an unsaturated side chain, and having an aldehydic carbonyl group or nitrile group at the free terminus of the side chain.
Compounds herein shown to be effective as attractants for notrhern corn rootworm include: estragole, trimethoxybenzene, 1,2,4-trimethoxybenzene, cinnamaldehyde, trans-cinnamaldehyde, cinnamonitrile, cinnamyl alcohol, cinnamyl acetate as well as 4-methylphenylethanol, 4-chlorophenylethanol, 4-fluorophenylethanol, phenylethanol, phenylpropanol, 4-methoxyphenylethanol, 3-methoxyphenylethanol, 2-methoxyphenylethanol, 4-methoxyphenylpropanol, phenylethylamine, and phenylpropylamine. Particularly useful NCR attractants are phenyl-propanoids such as (1) phenyl alkanols having a para-methoxy group and a 2- or 3-carbon alkanol, (2) phenyl alkanols with 2- or 3-carbon side chains including the unsaturated cinnamyl alcohol; and (3) phenyl alkylamines with 2- or 3-carbon side-chains.
Compounds shown herein to have particularly long term (persistent) effectiveness as NCR attractants include: phenyl propanol, phenylethyl amine, and 4-methoxyphenylethanol.
Compounds herein shown to be effective as attractants for Diabrotica cristata include: guaiacol, estragole, trimethoxybenzene, 1,2,4-trimethoxybenzene, indole, cinnamaldehyde, trans-cinnamaldehyde, xcex2-ionone, 4-methoxycinnamaldehyde, cinnamyl alcohol, and cinnamonitrile.
Attractant compounds and compositions of the invention attract both male and female rootworms and can be used with sticky traps and other types of insect traps at suitable attractive dosages, preferably ranging from approximately 1 mg to 100 mg per trap, although doses of 0.01 mg to 200 mg have been found to be effective, to attract hundreds of beetles per day. The VIP mixture attracts SCR adults at rates of 10 to 100 times greater than controls. The TIC mixture attracts WCR and SCR adults at rates of 10 to 100 times greater than controls. The CI mixture attracts WCR and SCR adults at rates of 10 to 100 times greater than controls. 4-Methoxycinnamaldehyde, 4-methoxycinnamonitrile, and xcex2-ionone attract WCR at rates 10 to 100 times controls; cinnamyl alcohol attracts NCR at rates 5-20 times controls; and cinnamaldehyde and cinnamonitrile atrract SCR at rates 5-20 times controls.
4-Methylphenylethanol, 4-chlorophenylethanol, 4-fluorophenylethanol, phenylethanol, phenylpropanol, 4-methoxyphenylethanol, 3-methoxyphenylethanol, 2-methoxyphenylethanol, 4-methoxyphenylpropanol, phenylethylamine, and phenylpropylamine attract NCR at rates approximately 5-50 times controls.
Attractants according to the invention may be used to manipulate adult corn rootworm behavior for monitoring and controlling corn rootworm populations. Through the use of these lures, a totally new technology for corn rootworm control is possible. By using these attractants, individually or in combination, the presence, species distribution, and reproductive state of adult corn rootworms can be monitored and pest management decisions be made for the next season infestation. Moreover, these attractants are so potent that they can mobilize adult corn rootworm populations in large fields and attract them to specific sites where they can be destroyed by spraying limited areas with conventional insecticides.
Alternatively, these lures can be used as components of a toxic bait for adult beetles. The toxic bait comprises: i) a Diabrotica species attractant, ii) a compulsive feeding stimulant, and iii) a diabroticiticidal insecticide. These baits can combine: i) as attractant, either the multi-component mixtures, e.g., VIP or TIC mixtures and/or the single component lures, e.g., eugenol, indole, veratrole, cinnamaldehyde, cinnamonitrile, cinnamyl alcohol, cinnamyl acetate;, 4-methoxycinnamaldehyde, 4-methoxycinnamonitrile, 4-methoxy-1-vinylbenzene, xcex2-ionone, trimethoxybenzene, phenylethanol, phenylpropanol, 4-methoxyphenyl ethanol, 4-methoxyphenyl propanol, phenylethylamine, phenylpropylamine and/or other compounds found in volatile fractions of blossoms of Cucurbita plants (the exact choice of lure depending on the relative economic importance of the three Diabrotica species); ii) as compulsive feeding stimulant, cucurbitacins obtained from, for example, bitter squash, and iii) as the diabroticiticidal insecticide, a relatively small dosage of a wide variety or conventional insecticides including organophosphorous, carbamate and pyrethroid insecticides, such as carbaryl, methomyl, isofenphos, malathion, and dimethoate. As used here the term diabroticiticidal includes a Diabrotica species insecticide and includes any and all compounds capable of killing Diabrotica species. (See, e.g., Canadian Patent 1,195,222 to R. L. Metcalf and A. M. Rhodes for the cucurbitacin-insecticide bait). This toxic bait combination of ingredients provides a long range and persistent (long term) attraction of beetles to a poison bait that acts as a contact feeding stimulant.
Other aspects and advantages of the present invention will be apparent upon consideration of the following detailed description thereof which includes numerous illustrative examples of the practice of the invention.
The following examples illustrate practice of the invention in the production of lures for attracting and controlling Diabrotics species. Specifically, the invention relates to lures comprising one or more compounds found in the volatile fraction of Cucurbita blossoms, or analogs thereof, alone or in combination with other lures, insecticides, and/or compulsive feeding stimulants.
Example 1 relates to the attraction of Diabrotica species to single-component and multi-component lures in corn fields.
Example 2 relates to the response of Diabrotica species (D. cristata and D. barberi) in a prairie habitat to eugenol analogs and to attractants for D. v. virgifera and D. barberi. 
Example 3 relates to the evaluation of twenty-four compounds, including estragole and estragole analogues, as attractants.
Example 4 relates to the preparation and use of poison (toxic) baits containing cucurbitacins, volatile attractants and insecticides.
Example 5 relates to Cucurbita blossom aroma and Diabrotica rootworm beetle attraction.
Example 6 relates to the evaluation of seven compounds, including phenylethanol analogues, as attractants.
The examples which follow are for illustrative purposes only and are not intended in any way to limit the scope of the invention.